S ub -S aharan A frica : F ood P roduction at R isk
(2011) anticipates modest reductions in these rates in the absence of climate change; with warming of 1.2–1.9°C by 2050,50 the proportion of the population that is undernourished is projected to increase by 25–90 percent compared to the present. The proportion of moderately stunted children, which ranges between 16–22 percent in the 2010 baseline, is projected to remain close to present levels in a scenario without climate change. With climate change, the rate is projected to increase approximately 9 percent above present levels. The proportion of severely stunted children, which ranges between 12–20 percent in the 2010 baseline, is expected to decrease absent climate change by approximately 40 percent across all regions. With climate change, this overall reduction from present levels would be only approximately 10 percent. The implications of these findings are serious, as stunting has been estimated to increase the chance of all-cause death by a factor of 1.6 for moderate stunting and 4.1 for severe stunting (Black et al. 2008). Other threats to health that are likely to be increased by climate change include fatalities and injuries due to extreme events or disasters such as flooding (McMichael and Lindgren 2011; World Health Organization 2009). An indirect health effect of flooding is the damage to key infrastructure. This was observed in a case in Kenya in 2009 when approximately 100,000 residents of the Tana Delta were cut off from medical services by floods that swept away a bridge linking the area with Ngao District Hospital (Daily Nation September 30, 2009, cited in Kumssa and Jones 2010). Another risk is heat stress resulting from higher temperatures. Lengthy exposure to high temperatures can cause heat-related illnesses, including heat cramps, fainting, heat exhaustion, heat stroke, and death. More frequent and intense periods of extreme heat have been linked to higher rates of illness and death in affected populations. The young, the elderly, and those with existing health problems are especially vulnerable. Heat extremes are expected to also particularly affect farmers and others engaged in outdoor labor without adequate protective measures (Myers 2012). The populations of inland African cities are expected to be particularly exposed to extreme heat events, as the built-up environment amplifies local temperatures (known as the “urban heat island effect”; UN Habitat 2011). However, as the heat extremes projected for Sub-Saharan Africa are unprecedented, the extent to which populations will be affected by or will be able to adapt to such heat extremes remains unknown. This remains an understudied area of climate-change-related impacts.
Vector and Water-borne Diseases Further risks to human health in Sub-Saharan Africa include the following: vector-borne diseases including malaria, dengue fever, leishmaniasis, Rift Valley fever, and schistosomiasis, and water and food-borne diseases, including cholera, dysentery and typhoid
fever, and diarrheal diseases; all of these diseases can be influenced by local climate (Costello et al. 2009). The diseases most sensitive to environmental changes are those that are vector-borne or food and water-borne. Flooding can be associated with outbreaks of diseases, such as cholera; while drought has been linked to such diseases as diarrhea, scabies, conjunctivitis, and trachoma (Patz et al. 2008). As cold-blooded arthropods (including mosquitoes, flies, ticks, and fleas) carry most vector-borne diseases, a marginal change in temperature can dramatically alter their populations. They are also highly sensitive to water and vegetation changes in their environment. Changes in these factors can, therefore, increase the incidence, seasonal transmission, and geographic range of many vector-borne diseases (Patz et al. 2008). The incidence of malaria is notoriously difficult to predict, There is great uncertainty about the role of environmental factors vis-à-vis endogenous, density-dependent factors in determining mosquito prevalence; many studies indicate, however, a correlation between increased malaria incidence and increased temperature and rainfall (Chaves and Koenraadt, 2010). In Botswana, for example, indices of ENSO-related climate variability have predicted malaria incidence (Thomson 2006); in Niger, total mosquito abundances showed strong seasonal patterns, peaking in August in connection with the Sahel water cycle (Caminade et al. 2011). This is consistent with observations that the drought in the Sahel in the 1970s resulted in a decrease in malaria transmission (Ermert, Fink, Morse, and Peeth 2012). Land-use patterns can also play a role in determining vector populations, with deforestation affecting temperature, and agricultural landscapes potentially providing suitable microhabitats for mosquito populations (Chaves and Koenraadt 2010). The areas where malaria is present is projected to change, with malaria pathogens potentially no longer surviving in some areas while spreading elsewhere into previously malaria-free areas. Even today malaria is spreading into the previously malaria-free highlands of Ethiopia, Kenya, Rwanda, and Burundi, with the frequency of epidemics there increasing, and may also enter the highlands of Somalia and Angola by the end of the century (Unmüßig and Cramer 2008). In the Sahel, the northern fringe of the malaria epidemic belt is projected to have shifted southwards (by 1–2 degrees) with a warming of 1.7°C by 2031–50 because of a projected decrease in the number of rainy days in the summer (Caminade et al. 2011); this means that it is possible that fewer people in the northern Sahel will be exposed to malaria. Outbreaks of Rift Valley fever (RVF), which are episodic, occur through mosquitos as the vector and infected domestic animals as secondary hosts and are linked to climate variability (including ENSO) (Anyamba et al. 2009). Intra-seasonal rainfall
50 The study use the NCAR and CSIRO scenarios, which project a temperature
increase of 1.9°C and 1.2°C above pre-industrial levels, respectively, by 2050.
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